Before you read this, I suggest you read post 17.13. In post 17.13, we met the idea of centripetal force – the force that is needed to pull an object to keep it moving round a circle. In post 17.28, we saw how the force exerted by the earth’s gravitational field provides the centripetal force… Continue reading 17.29 Centrifugal force

Before you read this, I suggest you read posts 16.16 and 17.13 Why does a satellite stay in orbit around the earth? If we think of something going round in a circle (like the hammer in post 17. 13 before it is thrown), it appears that something must be pulling it towards the earth. What… Continue reading 17.28 Satellites

Before you read this, I suggest you read posts 17.19, 16.20 and 16.16. But post 17.19, and this one, involve some mathematics that you might wish to ignore – so you may prefer not to read this post after the first few paragraphs! If a rocket is to be launched into space, it must take… Continue reading 17.27 Getting into space

  We have seen that planes fly because air provides “lift” under their wings (post 17.16); any engines that moves the plane forward will enable air to lift the plane. But there is no air in space (because air molecules are attracted to earth by its gravitational field – see post 16.16) so space-craft need… Continue reading 17.26 Rockets